The authorities stepped up repressive measures against Sunday’s Strategy 31 rally in defense of freedom of assembly in St. Petersburg, holding detained activists at police precincts overnight, searching activists’ apartments and investigating several participants for suspected extremism. If they are found guilty, they will face up to three years in prison.

Andrei Pivovarov, the local leader of the People’s Democratic Union (RNDS) and one of the rally’s organizers, was detained almost immediately after the start of the rally, taken to court three hours later and sentenced to 27 days in prison Sunday. The Other Russia’s Andrei Pesotsky was sentenced to 14 days in prison Monday.

Alexander Belenky/SPT. Police arrest a demonstrator by Gostiny Dvor on Nevsky Prospekt on Sunday. A total of 112 demonstrators were detained.

Andrei Dmitriyev, the local leader of The Other Russia party, was sentenced to five days in prison Monday after spending the night in a police precinct. They were all charged with violating the rules on holding public events and failing to obey a police officer’s orders.

Speaking on his cell phone from a police truck where he was held before the court hearing on Monday afternoon, Dmitriyev said that his apartment and those of two other activists were searched by the Center E anti-extremism state agency on Monday morning. The officers showed his parents documents stating that a criminal investigation had been opened into suspected participation in the activities of a banned organization.

The three activists whose apartments were searched — Dmitriyev, Vadim Mamedov and Alexander Yashin — are all members of The Other Russia, the party formed by author and oppositional politician Eduard Limonov earlier this year. Limonov’s previous party, the National Bolshevik Party (NBP), was banned as “extremist” in 2005.

Dmitriyev said that Center E is claiming that the NBP has been active in St. Petersburg during the past 18 months.

The police detained 104 people near Gostiny Dvor on Nevsky Prospekt, St. Petersburg’s main street, and another eight at a separate, smaller rally on Palace Square, organizers said. About 30 were held at three different police precincts throughout the night and taken to court on Monday.

Five activists, including The Other Russia’s Ravil Bashirov, had their cases postponed, but upon leaving the court, they were seized by plainclothes men and taken in for interrogation, The Other Russia activist Andrei Milyuk said by phone Monday. According to him, the interrogations were part of the investigation into the “extremism” case.

The OMON special-task police, whose faces were hidden behind ski masks and helmets, charged the crowd and detained speakers promptly, preventing them from speaking for more than a minute on Sunday. Pivovarov, who opened the rally, was among the first people to be detained, at 6 p.m. One of the last, Sergei Kuzin of the Solidarity democratic movement, was detained at 7:15 p.m.

During Sunday’s event, activists hung a large banner featuring anarchist symbols and the slogan “Any form of authority is shit. It’s forbidden to forbid,” from the roof of Passazh retail center directly opposite the rally’s location.

RNDS spokesman Pavel Smolyak said he believed that Pivovarov’s sentence was predetermined.

Smolyak said that Judge Alexei Kuznetsov declared the hearing “closed,” and Smolyak was not allowed into the courtroom during the hearing, which lasted two hours. “The policemen in the corridor reported [Pivovarov’s sentence] by phone before it was even announced; it was all obvious from the very start,” Smolyak said by phone Monday.

Strategy 31 is a nonpartisan civil rights campaign demanding that the authorities obey Article 31 of the Russian Constitution, which states that “citizens have the right to assemble peacefully, without weapons.” Proposed by Limonov last year, the events have been held on the 31st day of months that have that many days.

First held in Moscow on July 31 last year, the Strategy 31 events have been held in St. Petersburg since Jan. 31.

Sunday’s rally was not authorized by City Hall on the grounds that “planned maintenance work” would be in progress on the site near Gostiny Dvor at the time of the planned rally, organizers said. No work could be seen on Sunday.

The Strategy 31 events were held in 67 Russian cities, with support events in New York and London, The Other Russia’s spokesman Alexander Averin said Monday. Thirty-eight were detained in Moscow.